I would like to know the total effective number of cores in “Dell Precision 490 Workstation Dual Xeon Dual-Core 5140 2.33GHz 8GB 2x73GB 15K SAS DVD Windows XP Professional w/RAID.”
Like Tina said, it has four cores. Is something like this what you are referring too?
if it's really a dual dual-core, it has four cores.
However, Dell ships this machine as dual core (2) or quad core (4). So I don't know why you would find it advertised as dual dual-core (4).